1. Field of the Invention
The present invention relates to a radar device and a method for adjusting to remove radio wave interference occurring among radar sites.
2. Description of the Related Art
A radar device (hereinafter, referred to as interfered station) sometimes receives a radio wave (hereinafter, referred to as transmission signal) emitted from other adjacent radar devices (hereinafter, referred to as interfering station), or a radio wave (hereinafter, referred to as echo signal) emitted from the interfering station and reflected from a target. If a center frequency of the received signal is close If a center frequency of the received signal is close to a center frequency of a transmitted signal, interference occurs. Therefore, a conventional radar device has an interference wave removal function (“Revised Radar Technique” Supervised by Takashi Yoshida, Published by The Institute of Electronics, Information and Communication Engineers, Page 217). As an example of the interference wave removal function, there is a method for mutually amplitude-comparing echo signals at a prescribed distance in a continuous pulse repetition interval (PRI), assuming that an echo signal with a large amplitude difference as an interference wave, and replacing the echo signal with an amplitude value of the echo signal received in the last PRI.
However, in practice, if pulse repetition frequencies (PRFs) of the interfering stations are close to one another, or if the number of the interfering stations is large, a plurality of interference waves are resulted in continuous receptions and, these interference waves affect the precision of radar signal processing data.
As a related problem, in a radar device emitting transmission signals having a plurality of types of pulse widths and moderation methods, overlapping a secondary echo with a weak real echo signal makes it difficult the real echo signal.
Further, in a radar device using a plurality of types of transmission pulse signals, interference among pulse signals significantly affect the detection precision of the echo signal. For example, in a pulse compression radar device using a short pulse and a long pulse in the PRF, the short pulse for short range leaks into a long-range area, and it results in reducing the echo detection precision of the long pulse.
As mentioned above, in the conventional radar device, if pulse repetition frequencies (PRFs) of the interfering stations are close to one another, or if the number of the interfering stations is large, these interference waves affect on the precision of the radar signal processing data. Increasing the effect of the secondary echo reduces the detection precision of the real echo signal. Further, in the case of using a plurality of types of transmission pulse signals, the interference among the pulse signals significantly affect the detection precision of the echo signal.